Electric heating element



Aug. 16, 1927.

F. w. MOFFAT ELECTRIC HEATING ELEMENT Filed June a, 1926 INVENTDR.

Patented Au g. 16, 1927. a I UNITED STATES PATENT OFFICE.

FREDERICK W. MOFFAT, E WESTON, ONTARIO, CANADA.

ELECTRIC HEATING ELIF!IMETLITIJ.v

Application filed June 8,

element heats faster than the ordinary closed element and is cheaper, but the closedelement gives less trouble when a pot boils over.

devise a thoroughly reliable covered element, which will be cheaper to manufacture than the ordinary closed element and which will approximate the open element in. speed of heating.

I attain my object by forming the top of the element ;of a flat metal .disk having stifienin ribs formed on the under side. These ri s are preferably arranged to form one or more spiral grooves. In these 5 grooves are fitted a series of blocks of'porce:

lain or other material having the same characteristics of refractoriness and of insulating value at high temperatures. -These' blocks are adapted to support a coil of re- 0 sistance wiring so as to eifectively insulate it from the metal while interfering as little as possible with direct radiation from the wire' to the metal top. A metal pan supports the metal top and contains a disk of refractory 5 material which supports the porcelain blocks within the grooves of the top.

The device is constructed in detail substantially as hereinafter. more specifically described and as illustrated in the accompanying drawings in'which tion;

Fig. 2a plan view partly in section; Fig. -3 an end elevation of one of the porcelain blocks on a largerscale; and

Fig. 4 a plan view of the same.

In the drawings like numerals of reference.

indicate corresponding parts in the different figures. w 1 is the top of the element, wh1ch is i formed of a metal disk ribbed on its under" side to form a 'groove or grooves. In the.

form of my device shown in the drawings, I show two parallel spiral ribs 2 forming two grooves. Into these grooves I insert a series of porcelain blocks 3, preferably shaped as My object in the present invention is'to 1g. 1 is a side elevationpartly in sec- 1826. Serial No. 114,447.

segments of an annulus. These blocks are 'frusto-conical in cross section to better fit them'to the grooves which are necessarily tapered tofacilitate the drawing of the pattern'during the moulding of the top. 'Each block is formed with a longitudinal groove 4 in its upper side to receive the resistance wiring. When the blocksare all in positionasubstantiaIIy continuous channel for the wiring is formed. The actual contact of each block with adjacent blocks is not essen-' tial, however, as long as no gaps are left sufficient to permit of the sagging of the resistance wiring. lVhen unsupported, each block is formed with a bridge 5, whose function isv to prevent the resistance wiring springing up into contact with the metal.

top. These bridges are preferably as narrowas possible consistent with strength so as to interfere as little as possible with direct radiation from the resistance wiring to the top.

.I have specified the blocks as being formed of porcelain, which term, however, I intend to include any material having the same 1 properties of refractoriness and efliciency of electricalinsulations at all temperatures to which it is subjected in use.

As the porcelain blocks are applied to the top from below and are not anchored to the ribs 2, it is necessary to support them in position. To support these blocks I provide the disk 6 of refractory insulating material, which is supported in the pan 7 'the rim of which isaengaged by the rim, of the top 1.

The resistance wiring is of the usually coiled type and is strung through the blocks {3 under the bridges 5. The ends ofthe wir-- mg are carried downwardly through the disk 6.

Asin the construction shown in the drawings, there are two grooves in the under side of the top and two resistance wires. There are four wire ends brought down through The terminals 8 are carried by the hubs 9 of insulating material which project through the bottom of the pan and are secured there, to. Thecentral .hub 9 has two holes formed have one hole each through which the adja-' no cent ends of the resistance wires are brought for .connection to the terminals.

100 the disk6 for connection with the terminals.

While I have shown the element as provided with two spiral grooves, it is evident that one only may be used, or any other shape of groove or arrangement of grooves known to the art.

It will be seen that an element constructed as described is superior to the ordinary closed element, in that the resistance wiring is readily renewable. This element is also a quicker heating element than the ord nary closed element, in that the metal top is exposed to the direct radiation of the resistance wiring. The ribs on the under side of the top are adapted not only to stiifen the latter and prevent buckling but also serve to conduct heat from the porcelain blocks to the top, thus preventing over heating of the resistance wiring and carrying the heat quickly to the upper surface of the top where y it is effective for cooking purposes.

With the construction described I am enabled to employ porcelain as an insulation, which is much superior to the various cements used in the ordinary types of closed top. This construction is by virtue of its superior insulation specially adapted for use with high voltage current.

What I claim is:

1. An electric heating element comprising a metal disk ribbed to form a groove; a series of porcelain blocks fitted into said groove, each block being formed with .a groove to receive resistance Wiring; and a bridge adapted to retain the wire in the groove, the grooves forming a substantially continuous channel for the wiring.

2. An electric heating element comprising a metal disk ribbed to form a spiral groove; a series of porcelain blocks fitted into said groove, each block being formed with a groove to receive resistance wiring; and a bridge adapted to retain the wire in. the groove, the rooves forming a substantially continuous c annel for the wiring.

3. An electric heating element comprising a flat topped metal disk ribbed to form a groove at its under side; a series of porcelain blocks fitted into said groove, each block being formed with a groove in its upper side to receive resistance wiring; a bridge adapted to retain the wire in the groove, the grooves forming a substantially continuous channel for the wiring; and a support retaining said blocks in the groove.

4. An electric heating element comprising a flat topped metal disk ribbed to form a groove at its under side; a series of porcelain blocks fitted into said groove, each block being formed with a groove in its upper side to receive resistance wiring, the grooves forming a substantially continuous channel for the wiring; a metal pan; :1. disk of insulating refractory material supported by the pan and in turn supporting the porcelain blocks; and hubs of insulating material secured to and extending through the bottom of the pan and provided with holes for the passage of the ends of the resistance wiring.

5. An electric heating element comprising a fiat topped metal disk ribbed to form a groove at its under side; a series of porcelain blocks fitted into said groove, each block being formed with a groove in its upper side to receive resistance wiring, the grooves forming a substantially continuous channel for the wiring; a metal pan; a disk of insulating refractory material supported by the pan and in turn supporting the porcelain blocks; hubs of insulating material secured to and extending through the bottom of the pan and provided with holes for the passage Of the ends of the resistance wiring; and terminals to which the ends ofthe Wire are connected.

6. An electric heating element comprising a fiat topped metal disk; a series of porce-- lain blocks grooved in the upper sides and fitted end-to-end close to the under side of the disk, the grooves forming a substantially continuous channel for resistance wiring; a metal pan; a disk of insulating refractory material supported by the pan and in turn supporting the porcelain blocks; and hubs of insulating material secured to and extending through the bottom of the pan and provided with holes for the passage of the ends of the resistance wiring.

' 7. An electric heating element comprising a fiat topped metal disk; a series of porcelain blocks grooved in the upper sides and fitted end-to-end close to the under side of the disk, the grooves, forming a substantially continuous channel for resistance wiring; a metal pan; a disk of insulating refractory material supported by the pan and in turn supporting the porcelain blocks; hubs of insulating material secured to and extending throughthe bottom of the pan and provided with holes for the passage of the ends of the resistance wiring; and terminals to which the ends of thewire are connected.

8. An electric heating element comprising a metal disk ribbed to form a groove approximately rectilinear in cross section; a series of porcelain blocks fitted into said groove in contact with the sides thereof, .each block having a groove to receive resistance wiring formed. in the side facing the disk; and means for retaining the wiring in the grooves in the blocks without materially blocking radiation from the wiring to the disk, the grooves forming a channel for the wiring substantially entirely open adjacent the disk.

Signed at Toronto, Canada this 19th day of May, 1926.

FREDERICK W. MOFFAT. 

